Basler Electric MVC236 - Manual (Page 9)

9204300990 Rev J 3
Functional Description
The MVC 236 supplies power to the generator field through a phase-controlled, silicon-controlled rectifier
(SCR) bridge. By adjusting the remotely-mounted, manual voltage adjust control, the firing angle of the
SCR changes to provide an adjustable voltage level to the exciter field.
A simplified block diagram illustrating MVC 236 operation is shown in Figure 1.
Figure 1. MVC 236 Block Diagram
Operating Power
MVC 236 operating power can be supplied from a source with a nominal rating of 60 Vac, 120 Vac, or
240 Vac. The nominal source voltage is made on the MVC 236 through a tap selection.
The operating power frequency can be within one of three jumper-selectable ranges: 50 to 100 Hz, 100 to
200 Hz, or 200 to 400 Hz.
Buildup Circuit
During generator startup, the MVC 236 buildup circuit holds the SCR power bridge at maximum output.
Once the voltage builds to approximately 30 Vac, the buildup circuit relinquishes control to the remotely-
mounted, potentiometer for manual control of the field excitation level.
Auto/Manual Transfer
The available Auto/Off/Manual switch (P/N 9204306100) enables transfer from the automatic voltage
regulator to the MVC 236 and vice versa. Circuitry within the MVC 236 allows safe switching without the
risk of arcing.
Output Power
The jumper-selectable MVC 236 power output is rated for a nominal field voltage of 32 Vdc, 63 Vdc, or
125 Vdc.
Spike Suppression
Higher impedance sources, such as power isolation transformers and permanent magnet generators
(PMGs), may have enough inductance to produce damaging voltage spikes in the MVC 236 power output
stage. In these applications, use of the provided spike suppression module is recommended to filter out
Voltage Adjust
Error
Amplifier
Power
Supply
SCR
Control
Output Input
P0073-70
MVC 236 Functional Description